/*
 * Copyright (c) 2005, 2006, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package javax.lang.model.util;

import static javax.lang.model.SourceVersion.RELEASE_6;

import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.AnnotationValue;
import javax.lang.model.element.AnnotationValueVisitor;
import javax.lang.model.element.UnknownAnnotationValueException;

/**
 * A skeletal visitor for annotation values with default behavior appropriate
 * for the {@link SourceVersion#RELEASE_6 RELEASE_6} source version.
 * 
 * <p>
 * <b>WARNING:</b> The {@code AnnotationValueVisitor} interface implemented by
 * this class may have methods added to it in the future to accommodate new,
 * currently unknown, language structures added to future versions of the
 * Java&trade; programming language. Therefore, methods whose names begin with
 * {@code "visit"} may be added to this class in the future; to avoid
 * incompatibilities, classes which extend this class should not declare any
 * instance methods with names beginning with {@code "visit"}.
 * 
 * <p>
 * When such a new visit method is added, the default implementation in this
 * class will be to call the {@link #visitUnknown visitUnknown} method. A new
 * abstract annotation value visitor class will also be introduced to correspond
 * to the new language level; this visitor will have different default behavior
 * for the visit method in question. When the new visitor is introduced, all or
 * portions of this visitor may be deprecated.
 * 
 * @param <R>
 *            the return type of this visitor's methods
 * @param <P>
 *            the type of the additional parameter to this visitor's methods.
 * 
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ah&eacute;
 * @since 1.6
 */
@SupportedSourceVersion(RELEASE_6)
public abstract class AbstractAnnotationValueVisitor6<R, P> implements
		AnnotationValueVisitor<R, P> {

	/**
	 * Constructor for concrete subclasses to call.
	 */
	protected AbstractAnnotationValueVisitor6() {
	}

	/**
	 * Visits an annotation value as if by passing itself to that value's
	 * {@link AnnotationValue#accept accept}. The invocation {@code v.visit(av)}
	 * is equivalent to {@code av.accept(v, p)}.
	 * 
	 * @param av
	 *            {@inheritDoc}
	 * @param p
	 *            {@inheritDoc}
	 */
	public final R visit(AnnotationValue av, P p) {
		return av.accept(this, p);
	}

	/**
	 * Visits an annotation value as if by passing itself to that value's
	 * {@link AnnotationValue#accept accept} method passing {@code null} for the
	 * additional parameter. The invocation {@code v.visit(av)} is equivalent to
	 * {@code av.accept(v,
	 * null)}.
	 * 
	 * @param av
	 *            {@inheritDoc}
	 */
	public final R visit(AnnotationValue av) {
		return av.accept(this, null);
	}

	/**
	 * {@inheritDoc}
	 * 
	 * <p>
	 * The default implementation of this method in
	 * {@code AbstractAnnotationValueVisitor6} will always throw
	 * {@code UnknownAnnotationValueException}. This behavior is not required of
	 * a subclass.
	 * 
	 * @param av
	 *            {@inheritDoc}
	 * @param p
	 *            {@inheritDoc}
	 */
	public R visitUnknown(AnnotationValue av, P p) {
		throw new UnknownAnnotationValueException(av, p);
	}
}
